How are these produced? I assume they're not actually digging a giant trench and taking a section, but are the drawings based on measurements of a specific individual in some way? In any case, very cool to have such a collection.
They usually are. It’s a process akin to archaeology where they have to carefully wash away the dirt from the root system, measuring as they go. The problem with this method is that it's hard to reconstruct the entire 3d structure of bigger plants like trees so a lot of the root drawings on the site don’t accurately show how deep they go. It’s much easier with small plants where the researcher can control the soil us…
By “usually”, have you any examples of what led to that conclusion?